1. Field of the Invention
The present invention generally relates to fiber formation by electrospinning and, more particularly, to a new technique for the formation of polymeric fiber interconnections in very small (e.g., microscale or nanoscale) systems.
2. Background Description
Polymer fibers form the basis of a wide variety of industries ranging from breathable, weather-resistant, and bulletproof garments to telecommunications, structural engineering, and medicine. Polymer fibers are conventionally created by extruding a polymer melt through a spinneret and subsequently drawing the fibers as they coagulate. However, it is difficult to produce submicron diameter fibers using this conventional process and many emerging opportunities exist for high performance nanoscale materials and devices.
The recent focus on nanoscale engineering has revived interest in a radically different fiber formation technology known as electrospinning, wherein a polymer fiber is drawn from a solution using electrostatic instead of mechanical forces. The basic advantage of the electrospinning fiber formation process is that extremely small diameter, nanoscale fibers can be produced from a wide variety of polymer solutions (see, for example, Kenawy et al., Biomaterials 24:907 (2003); Deitzel et al, Polymer, 42:8163 (2001); and Reneker et al, Nanotechnology 7:216 (2000)). The theoretical model for the electrospinning process has evolved over time and the fiber formation mechanisms have been described in several recent articles (se, for example, Deitzel et al., Polymer 42:261 (2001); Yarin et al., J. App. Phys. 90:4836 (2001); and Shin et al., Polymer, 42:9955 (2001)). Typically, an electrospinning apparatus consists of a hypodermic syringe or needle filled with a polymer solution and placed at a high (approximately 15 kV) potential with respect to a ground plane. The sharp tip of the needle concentrates the electrostatic force and fibers emerge from the tip of a Taylor cone formed at the surface of the solution through a competition between electrostatic forces and surface tension. The fibers are collected at the counter electrode and typical electrospun structures consist of a nonwoven mat of fine fibers.